1. Field of the Invention
The present invention relates to a class of locking pliers, or vise grips in general, and more particularly to multi-purpose locking pliers with extendable clamping arms and threaded holes on clamping arms to attach a wide variety of clamping jaws and accessories. The invention is capable of clamping workpieces of various shapes such as rectangular, cylindrical, triangular, and spherical, etc. with adjustable clamping force. It is also capable of clamping workpieces within a broad range of sizes.
2. Description of the Related Art
A conventional locking plier or vise grip generally comprises a fixed arm with clamping jaw, a movable arm attached with clamping jaw and a toggling linkage mechanism attached between the movable arm and the fixed arm. To serve various applications, there are many different designs of the clamping jaws for locking pliers in the field, such as: C-shape clamping arm with round tips used in the Gripping Tool, U.S. Pat. No. 2,641,149; L-shape jaws used in Toe-nailing Clamping Tool, U.S. Pat. No. 4,305,575; V-shape jaws for cylindrical pipe clamping, U.S. Pat. No. 4,344,215; combination of wrench and chain clamping jaws, U.S. Pat. No. 4,477,937; long nose jaws for external and internal clamping, U.S. Pat. No. 4,542,669; combination of vise grip and bar clamp, U.S. Pat. No. 4,850,254; adjustable locking jaws, U.S. Pat. No. 5,022,290; C-shape arm with hole and clip, U.S. Pat. No. 5,469,766; adjustable locking bar clamp, U.S. Pat. No. 5,499,800; V-shape toothed jaws, U.S. Pat. No. 6,012,362; and cylindrical jaws for clamping various sizes pipes, U.S. Pat. No. 6,389,937; etc. However, almost all of these prior arts are single-purpose oriented, some of them may serve more than one purposes, but still very limited in application and flexibility. A number of locking pliers, each with different design features will be required to serve a number of different work holding jobs. Furthermore, the size of a workpiece that can be manipulated on is limited by the physical size of most of these prior arts. In other words, to clamp a workpiece of significantly different dimension will require a similar tool of the appropriate size. It is the intention of the present invention to provide a handy tool to work on workpieces within a broad range of physical sizes. Another intention is to enable the adjustment of the clamping force on a workpiece by turning an adjustment screw. Further intention of the present invention is to provide a convenient means to increase the clamping force on a workpiece by inserting a metal rod or any suitable screwdriver into the hole equipped on the adjustment screw to act as a handle to increase the turning torque. Yet another intention of the invention is to provide a simple means to adjust the workable gap between the clamping jaws of the invention. An additional intention of the present invention is to increase the functionality by attaching a wide variety of clamping jaws and accessories to work on workpieces of different shapes in various ways.